The present invention relates to the production of an insecticidal protein of Bacillus thuringiensis subsp. aizawai IPL by the DNA recombinant technology. More particularly, it relates to a gene coding for the insecticidal protein of Bacillus thuringiensis subsp. aizawai IPL, which has a potent insecticidal activity against noxious insects belonging to the order, Lepidoptera, such as larvae of diamond-back moth (Plutella maculipennis) and cotton cutworm (Spodoptera litura), and to an expression plasmid carrying the said gene and being capable of expressing the insecticidal protein in host cells. It also relates to a transformant microorganism harboring the said expression plasmid and being capable of producing the insecticidal protein, and to a process for producing the insecticidal protein comprising culturing the said transformant microorganism in a suitable medium.
It has been known that microorganisms classified as Bacillus thuringiensis produce 1-2 .mu.m in length of crystals of insecticidal protein in their sporulation phase, and that the insects that have eaten the protein stop eating and die from rupture of their intestines. Microorganisms belonging to Bacillus thuringiensis are further classified into 29 subspecies according to the flagella antigen, the esterase pattern and the like, and each of them exhibits a distinct and particular insecticidal activity.